WO2018070381A1 - Iron-based composite oxide catalyst for exhaust gas purification and method for producing same - Google Patents

Iron-based composite oxide catalyst for exhaust gas purification and method for producing same Download PDF

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WO2018070381A1
WO2018070381A1 PCT/JP2017/036679 JP2017036679W WO2018070381A1 WO 2018070381 A1 WO2018070381 A1 WO 2018070381A1 JP 2017036679 W JP2017036679 W JP 2017036679W WO 2018070381 A1 WO2018070381 A1 WO 2018070381A1
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fenbo
mass
catalyst
exhaust gas
iron
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PCT/JP2017/036679
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French (fr)
Japanese (ja)
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庸裕 田中
三郎 細川
謙太郎 寺村
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国立大学法人京都大学
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/89—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals
    • B01J23/8906—Iron and noble metals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/84—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/847—Vanadium, niobium or tantalum or polonium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/89—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0201—Impregnation
    • B01J37/0207—Pretreatment of the support
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/04—Mixing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/08—Heat treatment
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust

Definitions

  • the present invention relates to an iron-based composite oxide catalyst for exhaust gas purification and a method for producing the same, and more particularly, the development of a novel iron-based composite oxide catalyst for purifying automobile exhaust gas in a high oxygen concentration region (lean atmosphere) and It relates to the manufacturing method.
  • Automobile exhaust gas purification requires a main catalyst containing Pt, Rh, and Pd as noble metals and a co-catalyst of a CeO 2 -based composite oxide as an oxygen storage material (Non-patent Documents 1 and 2).
  • the role of the main catalyst is to purify harmful substances such as CO and NO contained in the exhaust gas and hydrocarbon (HC) as fuel residue into CO 2 , H 2 O, and N 2 . That is, in exhaust gas purification, it is necessary to proceed simultaneously with an oxidation reaction resulting from combustion of HC and CO and a reduction reaction for converting NO into N 2 . For this reason, the purification efficiency of harmful substances varies greatly depending on the oxygen concentration in the exhaust gas.
  • Non-Patent Document 3 This is because, under conditions where the air-fuel ratio is small (A / F ⁇ 14.6), the exhaust gas atmosphere is under reducing conditions, and HC and CO cannot be completely purified. On the other hand, under conditions where the air-fuel ratio is large (A / F> 14.6), it becomes an oxidizing atmosphere and it becomes difficult to purify NO. Based on this background, the development of a catalyst exhibiting high NO reduction activity under an oxygen-excess atmosphere (under a lean atmosphere) is regarded as an extremely important issue from the viewpoint of improving fuel efficiency.
  • An object of the present invention is to provide a catalyst having improved conversion of nitrogen oxides to nitrogen in exhaust gas in an oxidized state generated by lean burn.
  • the present invention provides the following iron-based composite oxide catalyst for exhaust gas purification and a method for producing the same.
  • Item 1 Formula (I) M / M 1 x O y / FeNbO 4 (I) (In the formula, M represents at least one noble metal selected from the group consisting of Pd, Rh and Pt. M 1 represents Mn or Fe. X represents an integer of 1 to 3, and y represents 2 to 4. When x is 1, y is 2, when x is 2, y is 3, and when x is 3, y is 4. The mass of M 1 x O y is FeNbO. 0 to 50% of the mass of 4.
  • M is supported on M 1 x O y / FeNbO 4
  • An iron-based composite oxide catalyst for exhaust gas purification represented by Item 2.
  • Item 6. The iron-based composite oxide catalyst for exhaust gas purification according to Item 1, wherein M is Rh.
  • Item 3. Item 3.
  • Item 6. The iron-based composite oxide catalyst for purifying exhaust gas according to Item 3, wherein the mass of Fe 2 O 3 is 15 to 25% of the mass of FeNbO 4 .
  • Item 5. M 1 x O y / FeNbO 4 (M 1 represents Mn or Fe.
  • X represents an integer of 1 to 3
  • y represents an integer of 2 to 4.
  • x is 1, y is 2.
  • x is 2, y is 3, and when x is 3, y is 4.
  • the mass of M 1 x O y is 0 to 50% of the mass of FeNbO 4 ).
  • the step of bringing the oxide carrier into contact with a solution containing at least one of a Pd compound, a Pt compound and an Rh compound, followed by firing, is carried out by the following formula (I) M / M 1 x O y / FeNbO 4 (I) (Wherein M represents at least one noble metal selected from the group consisting of Pd, Rh and Pt.
  • M 1 x O y is as defined above.
  • the mass of M 1 x O y is FeNbO 4. (M is supported on Fe 2 O 3 / FeNbO 4. )
  • the manufacturing method of the iron type complex oxide catalyst for exhaust gas purification represented by these.
  • a carrier supporting a noble metal (M) selected from the group consisting of Pd (palladium), Rh (rhodium) and Pt (platinum) is M 1 x O y / FeNbO 4 (M 1 , x, y As defined above, the mass of M 1 x O y is 0 to 50% of the mass of FeNbO 4 ).
  • M 1 x O y is 0 to 50% of the mass of FeNbO 4 ).
  • the iron-based composite oxide catalyst for exhaust gas purification of the present invention is useful as a three-way catalyst.
  • a schematic diagram of the three-way catalyst is shown in FIG.
  • the three-way catalyst includes hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOx), which are harmful components of exhaust gas, water (H 2 O), carbon dioxide (CO 2 ), which are harmless gases, It is a catalyst that converts to nitrogen (N 2 ).
  • the three-way catalyst of the present invention has a structure in which at least one kind of noble metal (Pt, Pd, Ph) is supported on a carrier represented by M 1 x O y / FeNbO 4 .
  • the supported amount of the noble metal M is preferably about 0.1 to 2%, more preferably 0.2 to 1.5, based on the mass of the composite oxide support represented by M 1 x O y / FeNbO 4. %, More preferably about 0.5 to 1.5%, particularly preferably about 0.8 to 1.2%.
  • a smaller amount of noble metal supported is preferable because the cost is reduced. However, if the amount is too small, there is a risk that the NO reduction activity is reduced.
  • the noble metal M supported on the composite oxide support includes at least one selected from the group consisting of Pd, Rh and Pt, preferably Pd, Rh or Pt, more preferably Pd or Rh, most preferably Is Rh.
  • M 1 x O y includes five types of iron oxide or manganese oxide of MnO 2 , Mn 2 O 3 , Fe 2 O 3 , Mn 3 O 4 , Fe 3 O 4 , preferably MnO 2 , Mn 2 O 3 and Fe 2 O 3 , particularly preferably Fe 2 O 3 .
  • the carrier of the present invention is composed of FeNbO 4 and M 1 x O y (M 1 , x, and y are as defined above).
  • the mass of M 1 x O y is 0 to 50% of the mass of FeNbO 4 .
  • the lower limit of the mass of M 1 x O y is 0%, 1%, 2%, 3%, 5%, 7%, 10%, 12% or 15% of the mass of FeNbO 4
  • the upper limit is 50% 45%, 40%, 35%, 30% or 25%.
  • the mass of M 1 x O y is preferably 0 to 40%, more preferably 10 to 30%, and further preferably 15 to 25% of the mass of FeNbO 4 .
  • the iron-based composite oxide catalyst for exhaust gas purification of the present invention becomes M / FeNbO 4 .
  • M 1 x O when y mass is less than 50% greater than 0% of the mass of FeNbO 4 of, FeNbO 4 and M 1 x O y may be generated simultaneously by firing but, Fe compound FeNbO 4 or Mn
  • a composite oxide carrier of the present invention composed of FeNbO 4 and M 1 x O y (M 1 , x, and y are as defined above) can be produced by supporting and firing a compound. Is possible.
  • Fe compounds include organic acid salts such as nitrates and acetates, carbonates, halides (fluorides, chlorides, bromides, iodides), acetylacetone, alkoxides (methoxide, ethoxide, tert-butoxide, etc.)
  • organic acid salts such as nitrates and acetates
  • carbonates halides (fluorides, chlorides, bromides, iodides), acetylacetone, alkoxides (methoxide, ethoxide, tert-butoxide, etc.)
  • halides fluorides, chlorides, bromides, iodides
  • acetylacetone alkoxides (methoxide, ethoxide, tert-butoxide, etc.)
  • alkoxides methoxide, ethoxide, tert-butoxide, etc.
  • Mn compounds include organic acid salts such as nitrates and acetates, carbonates, halides (fluorides, chlorides, bromides, iodides), acetylacetone, alkoxides (methoxide, ethoxide, tert-butoxide, etc.)
  • a complex compound in which a ligand is coordinated, an organic acid salt such as acetate, and a nitrate can be preferably used.
  • the firing temperature is about 400 ° C. to 1000 ° C., preferably about 500 to 700 ° C.
  • the firing time is about 10 minutes to 24 hours, preferably about 30 minutes to 5 hours. Firing can be performed under air flow.
  • Catalyst represented by the general formula (I) of the present invention the solution containing the noble metal compound M 1 x O y / FeNbO 4 (M 1, x, y are as defined above .M 1 x O
  • the mass of y is 0 to 50% of the mass of FeNbO 4 ).
  • the composite oxide carrier represented by (2) is impregnated or immersed, or a solution containing a noble metal compound is applied to the carrier by spraying or the like. Then, it can manufacture by baking.
  • platinum compounds such as hexachloroplatinic acid, tetrachloroplatinic acid, potassium tetrachloroplatinate, sodium tetrachloroplatinate, platinum chloride, dinitrodiamineplatinum; palladium chloride, palladium nitrate, palladium sulfate, palladium acetate, etc.
  • Palladium compounds; rhodium compounds such as rhodium chloride, rhodium sulfate, rhodium nitrate, rhodium hydroxide and acetylacetonatodium.
  • the firing temperature is about 400 ° C. to 1000 ° C., preferably about 500 to 700 ° C.
  • the firing time is about 10 minutes to 24 hours, preferably about 30 minutes to 5 hours. Firing can be performed under air flow.
  • the catalyst of the present invention can treat CO, hydrocarbon (HC) and NOx under lean burn conditions, it is particularly excellent as a three-way catalyst for automobile exhaust gas purification.
  • Example 1 To FeNbO 4 obtained in Reference Production Example 1, the amount is 10 mass% of Fe 2 O 3 after firing 20 wt%, 30 wt%, the amount of Fe (NO 3) becomes 50 mass% 3 ⁇ 9H 2
  • An aqueous solution containing O is impregnated with FeNbO 4 (1 g), fired at 500 ° C., 10 Fe 2 O 3 / FeNbO 4 , 20 Fe 2 O 3 / FeNbO 4 , 30 Fe 2 O 3 / FeNbO 4 , 50 Fe 2 O
  • a composite oxide carrier represented by 3 / FeNbO 4 was obtained.
  • Rhodium acetylacetonate (III) Rh
  • Rhodium acetylacetonate (III) (Rh) so that Rh is 1.0 wt% as a metal with respect to ⁇ -Al 2 O 3 (reference catalyst ALO-7 (180 m 2 / g), provided by the Catalysis Society of Japan, 0.99 g).
  • (Acac) 3 , 0.0401 g) was impregnated and supported in a 9 ml ethyl acetate solution, dried, and then calcined in air at 500 ° C. for 30 minutes to obtain 1 wt% Rh / Al 2 O 3 .
  • Comparative Examples 2-6 1 wt% Rh / Fe 2 O 3 (Comparative Example 3), 1 wt% Rh / 20Fe 2 O 3 / CeO 2 (Comparative Example 4) in the same manner as in Comparative Example 1 except that the metal oxide catalyst used is changed. 1 wt% Rh / 20Fe 2 O 3 / ZrO 2 (Comparative Example 5) and 1 wt% Rh / 20Fe 2 O 3 / Al 2 O 3 (Comparative Example 6) were prepared.
  • Test example 1 The 1 wt% Rh / Al 2 O 3 and 1 wt% Rh / FeNbO 4 catalysts obtained in Comparative Examples 1 and 2 were reacted using an atmospheric pressure fixed bed flow reactor schematically shown in FIG. .
  • a catalyst 200 mg was filled in a quartz reaction tube, and as a pretreatment, He was allowed to flow at 30 mL min ⁇ 1 at 500 ° C. for 1 h.
  • reaction gases NO: 1000 ppm, CO: 1000 ppm, C 3 H 6 : 250 ppm, O 2 : (1462 ppm ⁇ 1125 ppm ⁇ 675 ppm ⁇ 1125 ppm ⁇ 1462 ppm), He: balance mixed gas is circulated to the catalyst layer at 100 mL min ⁇ 1 I let you.
  • the stoichiometric amount of oxygen was 1125 ppm, and in the experiment for varying the oxygen concentration, the concentrations of NO, CO, and C 3 H 6 were fixed.
  • the outlet gas analysis was performed after changing from a high oxygen concentration to a low oxygen concentration and holding for 30 minutes at each oxygen concentration condition when the oxygen concentration was changed again to a high oxygen concentration.
  • Test example 2 The 1 wt% Rh / FeNbO 4 obtained in Example 1 and the 1 wt% Rh / Al 2 O 3 catalyst obtained in Comparative Example 1 were tested using the catalyst shown in FIG.
  • a catalyst 200 mg was filled in a quartz reaction tube, and as a pretreatment, He was allowed to flow at 30 mL min ⁇ 1 at 500 ° C. for 1 h.
  • a catalyst 200 mg was filled in a quartz reaction tube, and as a pretreatment, He was allowed to flow at 30 mL min ⁇ 1 at 500 ° C. for 1 h.
  • the analysis of the reaction gas was performed by two TCD-GC8A (MS-5A and Porapak Q manufactured by Shimadzu). C 3 H 6 , CO, CO 2 , N 2 and N 2 O were measured by two TCD-GC8A (MS-5A and Porapak Q), and the conversion efficiency from NO to N 2 was determined. The results are shown in FIG. 4 and FIG. Was examined supporting amount effect of Fe 2 O 3, it revealed that carrying 20 wt% Fe 2 O 3 1wt% Rh / Fe 2 O 3 / FeNbO 4 is longest maintaining high activity. Further, when the carrier was changed from FeNbO 4 to various carriers, the retention time of all the carriers was lower than that of FeNbO 4 .
  • the XRD pattern was measured for each 2 O 3 catalyst. The results are shown in FIG. In 1 wt% Rh / Fe 2 O 3 / FeNbO 4 supporting 20 mass% or more of Fe 2 O 3 , a peak of ⁇ -Fe 2 O 3 was observed in addition to FeNbO 4 having an ⁇ -PbO 2 type structure.
  • Test Example 5 Obtained in Example 1 was 1wt% Rh / 20 Fe 2 O 3 / FeNbO 4, Comparative Example 3 1 wt% was obtained at a Rh / Fe 2 O 3, FeNbO 4 and ⁇ -Fe 2 O 3 obtained in Reference Production Example 1
  • a catalyst (200 mg) was filled in a quartz reaction tube, and as a pretreatment, He was allowed to flow at 30 mL min ⁇ 1 at 500 ° C. for 1 h.
  • Example 1 In 1wt% Rh / 20 Fe 2 O 3 / FeNbO 4 obtained in Comparative Example 3 1 wt% was obtained at a Rh / Fe 2 O 3, and FeNbO 4 obtained in Reference Production Example 1 ⁇ ⁇ -Fe 2 O An XRD pattern was measured for a catalyst in which 1 wt% Rh was supported on a support obtained by physically mixing 3 in a weight ratio of 80:20. The results are shown in FIG. Compared to the physical mixture catalyst, the peak intensity of the person carrying the Fe 2 O 3 in FeNbO 4 impregnated carrier is Fe 2 O 3 is small, the high activity of carrying a Fe 2 O 3 nano-sized FeNbO 4 It was suggested that this is one of the factors to maintain.
  • Test Example 7 The oxygen storage capacity of the 1 wt% Rh / FeNbO 4 and 1 wt% Rh / 20 Fe 2 O 3 / FeNbO 4 obtained in Example 1 and the 1 wt% Rh / Fe 2 O 3 catalyst obtained in Comparative Example 3 was measured. .
  • the catalyst 100 mg was set in an alumina cell for thermogravimetric analysis (TG-820, manufactured by Rigaku). 5% O 2 / Ar as a reaction gas was passed through the catalyst layer at 100 mL min ⁇ 1 and the temperature was raised to 500 ° C. After holding in a 5% O 2 / Ar atmosphere for 30 minutes, 5% H 2 / Ar was switched to a gas of 100 mL min ⁇ 1 and the change in weight was measured for 20 minutes.
  • TG-820 thermogravimetric analysis

Abstract

The present invention provides an iron-based composite oxide catalyst for exhaust gas purification, which is represented by formula (I). M/M1 xOy/FeNbO4 (I) (In the formula, M, M1, x and y are as defined in the description.)

Description

排ガス浄化用鉄系複合酸化物触媒及びその製造方法Iron-based composite oxide catalyst for exhaust gas purification and method for producing the same
　本発明は，排ガス浄化用鉄系複合酸化物触媒及びその製造方法に関するものであり，詳しくは高酸素濃度域（リーン雰囲気）での自動車排ガス浄化を指向した新規鉄系複合酸化物触媒の開発及びその製造方法に関するものである。 The present invention relates to an iron-based composite oxide catalyst for exhaust gas purification and a method for producing the same, and more particularly, the development of a novel iron-based composite oxide catalyst for purifying automobile exhaust gas in a high oxygen concentration region (lean atmosphere) and It relates to the manufacturing method.
　自動車排気ガス浄化には，貴金属であるＰｔ，Ｒｈ，Ｐｄを含んだ主触媒と酸素貯蔵材料であるＣｅＯ２系複合酸化物の助触媒が必要とされている（非特許文献１および２）。主触媒の役割は排ガス中に含まれているＣＯ，ＮＯ，燃料残渣である炭化水素（ＨＣ）などの有害物質をＣＯ２，Ｈ２Ｏ，Ｎ２へと浄化することである。すなわち，排ガス浄化には，ＨＣおよびＣＯの燃焼に起因する酸化反応とＮＯをＮ２に変換する還元反応を同時に進行させる必要がある。そのため，排ガス中の酸素濃度に応じて，有害物質の浄化効率は大きく変動する。その中でも，有害物質を効率よく浄化するためには，燃料が完全燃焼し，かつ，酸素の残らない理論空燃比（Ｔｈｅｏｒｅｔｉｃａｌ　Ａｉｒ　Ｆｕｅｌ　ｒａｔｉｏ：　Ａ／Ｆ＝１４．６）近傍であることが望ましいとされている（非特許文献３）。なぜなら，空燃比が小さい条件（Ａ／Ｆ＜１４．６）では，排ガスの雰囲気は還元条件下となり，ＨＣおよびＣＯは完全には浄化できない。一方，空燃比が大きい条件（Ａ／Ｆ＞１４．６）では，酸化雰囲気下となりＮＯの浄化が困難となってしまう。このような背景の基，酸素過剰雰囲気下（リーン雰囲気下）で高いＮＯ還元活性を示す触媒の開発は，燃費向上の観点から極めて重要な課題とされている。 Automobile exhaust gas purification requires a main catalyst containing Pt, Rh, and Pd as noble metals and a co-catalyst of a CeO 2 -based composite oxide as an oxygen storage material (Non-patent Documents 1 and 2). The role of the main catalyst is to purify harmful substances such as CO and NO contained in the exhaust gas and hydrocarbon (HC) as fuel residue into CO 2 , H 2 O, and N 2 . That is, in exhaust gas purification, it is necessary to proceed simultaneously with an oxidation reaction resulting from combustion of HC and CO and a reduction reaction for converting NO into N 2 . For this reason, the purification efficiency of harmful substances varies greatly depending on the oxygen concentration in the exhaust gas. Among them, in order to efficiently purify harmful substances, it is desirable that the fuel is completely burned and that the vicinity of the theoretical air fuel ratio (A / F = 14.6) where oxygen does not remain is desirable. (Non-Patent Document 3). This is because, under conditions where the air-fuel ratio is small (A / F <14.6), the exhaust gas atmosphere is under reducing conditions, and HC and CO cannot be completely purified. On the other hand, under conditions where the air-fuel ratio is large (A / F> 14.6), it becomes an oxidizing atmosphere and it becomes difficult to purify NO. Based on this background, the development of a catalyst exhibiting high NO reduction activity under an oxygen-excess atmosphere (under a lean atmosphere) is regarded as an extremely important issue from the viewpoint of improving fuel efficiency.
　本発明は、リーンバーンで生じる酸化状態の排ガスにおいて、窒素酸化物から窒素への変換を向上した触媒を提供することを目的とする。 An object of the present invention is to provide a catalyst having improved conversion of nitrogen oxides to nitrogen in exhaust gas in an oxidized state generated by lean burn.
　本発明は、以下の排ガス浄化用鉄系複合酸化物触媒及びその製造方法を提供するものである。
項１．　下記式（Ｉ）
　Ｍ／Ｍ１ ｘＯｙ／ＦｅＮｂＯ４　　　（Ｉ）
（式中、ＭはＰｄ、Ｒｈ及びＰｔからなる群から選ばれる少なくとも１種の貴金属を示す。Ｍ１は、ＭｎもしくはＦｅを示す。ｘは１～３の整数を示し、ｙは２～４の整数を示す。ｘが１のときはｙが２であり，ｘが２のときはｙが３であり，ｘが３のときはｙが４である。Ｍ１ ｘＯｙの質量はＦｅＮｂＯ４の質量の０～５０％である。Ｍは、Ｍ１ ｘＯｙ／ＦｅＮｂＯ４に担持されている。）
で表わされる、排ガス浄化用鉄系複合酸化物触媒。
項２．　ＭがＲｈである、項１に記載の排ガス浄化用鉄系複合酸化物触媒。
項３．　Ｍ１ ｘＯｙがＦｅ２Ｏ３である、項１又は２に記載の排ガス浄化用鉄系複合酸化物触媒。
項４．　Ｆｅ２Ｏ３の質量はＦｅＮｂＯ４の質量の１５～２５％である、項３に記載の排ガス浄化用鉄系複合酸化物触媒。
項５．　Ｍ１ ｘＯｙ／ＦｅＮｂＯ４（Ｍ１は、ＭｎもしくはＦｅを示す。ｘは１～３の整数を示し、ｙは２～４の整数を示す。ｘが１のときはｙが２であり，ｘが２のときはｙが３であり，ｘが３のときはｙが４である。Ｍ１ ｘＯｙの質量はＦｅＮｂＯ４の質量の０～５０％である。）で表わされる複合酸化物担体をＰｄ化合物、Ｐｔ化合物及びＲｈ化合物の少なくとも１種を含む溶液に接触し、焼成する工程
を含む、下記式（Ｉ）
　Ｍ／Ｍ１ ｘＯｙ／ＦｅＮｂＯ４　　　（Ｉ）
（式中、ＭはＰｄ、Ｒｈ及びＰｔからなる群から選ばれる少なくとも１種の貴金属を示す。Ｍ１ ｘＯｙは前記に定義されるとおりである。Ｍ１ ｘＯｙの質量はＦｅＮｂＯ４の質量の０～５０％である。Ｍは、Ｆｅ２Ｏ３／ＦｅＮｂＯ４に担持されている。）
で表わされる、排ガス浄化用鉄系複合酸化物触媒の製造方法。 The present invention provides the following iron-based composite oxide catalyst for exhaust gas purification and a method for producing the same.
Item 1. Formula (I)
M / M 1 x O y / FeNbO 4 (I)
(In the formula, M represents at least one noble metal selected from the group consisting of Pd, Rh and Pt. M 1 represents Mn or Fe. X represents an integer of 1 to 3, and y represents 2 to 4. When x is 1, y is 2, when x is 2, y is 3, and when x is 3, y is 4. The mass of M 1 x O y is FeNbO. 0 to 50% of the mass of 4. M is supported on M 1 x O y / FeNbO 4 )
An iron-based composite oxide catalyst for exhaust gas purification represented by
Item 2. Item 6. The iron-based composite oxide catalyst for exhaust gas purification according to Item 1, wherein M is Rh.
Item 3. Item 3. The iron-based composite oxide catalyst for exhaust gas purification according to Item 1 or 2, wherein M 1 x O y is Fe 2 O 3 .
Item 4. Item 6. The iron-based composite oxide catalyst for purifying exhaust gas according to Item 3, wherein the mass of Fe 2 O 3 is 15 to 25% of the mass of FeNbO 4 .
Item 5. M 1 x O y / FeNbO 4 (M 1 represents Mn or Fe. X represents an integer of 1 to 3, y represents an integer of 2 to 4. When x is 1, y is 2. , When x is 2, y is 3, and when x is 3, y is 4. The mass of M 1 x O y is 0 to 50% of the mass of FeNbO 4 ). The step of bringing the oxide carrier into contact with a solution containing at least one of a Pd compound, a Pt compound and an Rh compound, followed by firing, is carried out by the following formula (I)
M / M 1 x O y / FeNbO 4 (I)
(Wherein M represents at least one noble metal selected from the group consisting of Pd, Rh and Pt. M 1 x O y is as defined above. The mass of M 1 x O y is FeNbO 4. (M is supported on Fe 2 O 3 / FeNbO 4. )
The manufacturing method of the iron type complex oxide catalyst for exhaust gas purification represented by these.
　本発明によれば、Ｐｄ（パラジウム）、Ｒｈ（ロジウム）及びＰｔ（白金）からなる群から選ばれる貴金属（Ｍ）を担持する担体をＭ１ ｘＯｙ／ＦｅＮｂＯ４（Ｍ１、ｘ、ｙは前記に定義されるとおりである。Ｍ１ ｘＯｙの質量はＦｅＮｂＯ４の質量の０～５０％である。）とすることで、リーンバーンによる酸化状態の燃焼が続いた酸化雰囲気の排ガスにおいて、ＣＨ，ＣＯだけでなく、ＮＯからＮ２への高効率の変換が行われる。また、長時間酸化雰囲気でＮＯからＮ２への変換を行うと変換効率が低下するが、そのような触媒は、いったん還元雰囲気にすると再びＮＯからＮ２への変換効率は向上する。 According to the present invention, a carrier supporting a noble metal (M) selected from the group consisting of Pd (palladium), Rh (rhodium) and Pt (platinum) is M 1 x O y / FeNbO 4 (M 1 , x, y As defined above, the mass of M 1 x O y is 0 to 50% of the mass of FeNbO 4 ). , Not only CH and CO, but also highly efficient conversion from NO to N 2 is performed. Further, when NO is converted to N 2 in an oxidizing atmosphere for a long time, the conversion efficiency is lowered. However, once such a catalyst is brought into a reducing atmosphere, the conversion efficiency from NO to N 2 is improved again.
三元触媒反応の反応条件Reaction conditions for three-way catalytic reaction ＮＯからＮ２への変換率の酸素濃度依存性Dependence of oxygen concentration on the conversion rate from NO to N 2 リーン条件（λ＝１．１６）からリッチ条件（λ＝０．７９）さらにリーン条件（λ＝１．１６）に変化させたときのＮＯからＮ２への変換率の経時変化Change with time of conversion rate from NO to N 2 when changing from lean condition (λ = 1.16) to rich condition (λ = 0.79) and further to lean condition (λ = 1.16) リッチ条件（λ＝０．７９）を経験させた後の触媒におけるリーン条件下（λ＝１．１６）での触媒活性：Ｆｅ２Ｏ３担持量の効果Catalyst activity under the lean condition (λ = 1.16) in the catalyst after experiencing the rich condition (λ = 0.79): effect of Fe 2 O 3 loading リッチ条件（λ＝０．７９）を経験させた後の触媒におけるリーン条件下（λ＝１．１６）での触媒活性：担体の比較Catalyst activity under lean conditions (λ = 1.16) in the catalyst after experiencing rich conditions (λ = 0.79): comparison of supports 各触媒のＸＲＤパターンXRD pattern of each catalyst リッチ条件（λ＝０．７９）を経験させた後の触媒におけるリーン条件下（λ＝１．１６）での触媒活性：物理混合触媒の比較Catalyst activity under lean conditions (λ = 1.16) in catalysts after experiencing rich conditions (λ = 0.79): Comparison of physical mixed catalysts 各触媒のＸＲＤパターンXRD pattern of each catalyst 各触媒の酸素貯蔵能（ＯＳＣ）測定Measurement of oxygen storage capacity (OSC) of each catalyst
　本明細書において、
「１Ｒｈ／１０Ｍ１ ｘＯｙ／ＦｅＮｂＯ４」は、Ｍ１ ｘＯｙの質量はＦｅＮｂＯ４の１０質量％であり、かつ、Ｒｈの質量は、Ｍ１ ｘＯｙ／ＦｅＮｂＯ４の１質量％であることを示し、
「１Ｒｈ／２０Ｍ１ ｘＯｙ／ＦｅＮｂＯ４」は、Ｍ１ ｘＯｙの質量はＦｅＮｂＯ４の２０質量％であり、かつ、Ｒｈの質量は、Ｍ１ ｘＯｙ／ＦｅＮｂＯ４の１質量％であることを示し、
「１Ｒｈ／３０Ｍ１ ｘＯｙ／ＦｅＮｂＯ４」は、Ｍ１ ｘＯｙの質量はＦｅＮｂＯ４の３０質量％であり、かつ、Ｒｈの質量は、Ｍ１ ｘＯｙ／ＦｅＮｂＯ４の１質量％であることを示し、
「１Ｒｈ／５０Ｍ１ ｘＯｙ／ＦｅＮｂＯ４」は、Ｍ１ ｘＯｙの質量はＦｅＮｂＯ４の５０質量％であり、かつ、Ｒｈの質量は、Ｍ１ ｘＯｙ／ＦｅＮｂＯ４の１質量％であることを示す（Ｍ１、ｘ、ｙは前記に定義されるとおりである）。 In this specification,
In “1Rh / 10M 1 x O y / FeNbO 4 ”, the mass of M 1 x O y is 10% by mass of FeNbO 4 , and the mass of Rh is 1 % by mass of M 1 x O y / FeNbO 4. Indicating that
In “1Rh / 20M 1 x O y / FeNbO 4 ”, the mass of M 1 x O y is 20 mass% of FeNbO 4 , and the mass of Rh is 1 mass% of M 1 x O y / FeNbO 4. Indicating that
In “1Rh / 30M 1 x O y / FeNbO 4 ”, the mass of M 1 x O y is 30% by mass of FeNbO 4 , and the mass of Rh is 1 % by mass of M 1 x O y / FeNbO 4. Indicating that
In “1Rh / 50M 1 x O y / FeNbO 4 ”, the mass of M 1 x O y is 50 mass% of FeNbO 4 , and the mass of Rh is 1 mass% of M 1 x O y / FeNbO 4. (M 1 , x, and y are as defined above).
　また、「λ」は図１で示される式で計算される反応条件の酸素濃度の指標であり、λ＝１が化学量論状態、λ＞１が酸化雰囲気（酸素過剰）、λ＜１が還元雰囲気（酸素不足）である。 “Λ” is an index of the oxygen concentration of the reaction condition calculated by the equation shown in FIG. 1, where λ = 1 is the stoichiometric state, λ> 1 is the oxidizing atmosphere (oxygen excess), and λ <1 is It is a reducing atmosphere (oxygen deficiency).
　本発明の排ガス浄化用鉄系複合酸化物触媒は、三元触媒として有用である。三元触媒の模式図を図１に示す。三元触媒は、排気ガスの有害成分である炭化水素（ＨＣ）、一酸化炭素（ＣＯ）、窒素酸化物（ＮＯｘ）を無害ガスである水（Ｈ２Ｏ）、二酸化炭素（ＣＯ２）、窒素（Ｎ２）に変換する触媒である。 The iron-based composite oxide catalyst for exhaust gas purification of the present invention is useful as a three-way catalyst. A schematic diagram of the three-way catalyst is shown in FIG. The three-way catalyst includes hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOx), which are harmful components of exhaust gas, water (H 2 O), carbon dioxide (CO 2 ), which are harmless gases, It is a catalyst that converts to nitrogen (N 2 ).
　本発明の三元触媒は、Ｍ１ ｘＯｙ／ＦｅＮｂＯ４で表される担体に少なくとも１種の貴金属（Ｐｔ，Ｐｄ，Ｐｈ）が担持された構造を有する。 The three-way catalyst of the present invention has a structure in which at least one kind of noble metal (Pt, Pd, Ph) is supported on a carrier represented by M 1 x O y / FeNbO 4 .
　貴金属Ｍの担持量は、Ｍ１ ｘＯｙ／ＦｅＮｂＯ４で表される複合酸化物担体の質量を基準にして、好ましくは０．１～２％程度、より好ましくは０．２～１．５％程度、さらに好ましくは０．５～１．５％程度、特に好ましくは０．８～１．２％程度である。貴金属の担持量は少ないほどコストが低減されて好ましいが、あまりに少なすぎるとＮＯ還元活性の低下を伴うリスクがある。 The supported amount of the noble metal M is preferably about 0.1 to 2%, more preferably 0.2 to 1.5, based on the mass of the composite oxide support represented by M 1 x O y / FeNbO 4. %, More preferably about 0.5 to 1.5%, particularly preferably about 0.8 to 1.2%. A smaller amount of noble metal supported is preferable because the cost is reduced. However, if the amount is too small, there is a risk that the NO reduction activity is reduced.
　複合酸化物担体に担持される貴金属Ｍとしては、Ｐｄ、Ｒｈ及びＰｔからなる群から選ばれる少なくとも１種が挙げられ、好ましくはＰｄ、Ｒｈ又はＰｔであり、より好ましくはＰｄ又はＲｈ、最も好ましくはＲｈである。 The noble metal M supported on the composite oxide support includes at least one selected from the group consisting of Pd, Rh and Pt, preferably Pd, Rh or Pt, more preferably Pd or Rh, most preferably Is Rh.
　Ｍ１ ｘＯｙは、ＭｎＯ２、Ｍｎ２Ｏ３、Ｆｅ２Ｏ３、Ｍｎ３Ｏ４、Ｆｅ３Ｏ４、の５種の酸化鉄又は酸化マンガンが含まれ、好ましくはＭｎＯ２、Ｍｎ２Ｏ３、Ｆｅ２Ｏ３、特に好ましくはＦｅ２Ｏ３である。 M 1 x O y includes five types of iron oxide or manganese oxide of MnO 2 , Mn 2 O 3 , Fe 2 O 3 , Mn 3 O 4 , Fe 3 O 4 , preferably MnO 2 , Mn 2 O 3 and Fe 2 O 3 , particularly preferably Fe 2 O 3 .
　本発明の担体は、ＦｅＮｂＯ４とＭ１ ｘＯｙ（Ｍ１、ｘ、ｙは前記に定義されるとおりである）から構成される。Ｍ１ ｘＯｙの質量は、ＦｅＮｂＯ４の質量の０～５０％である。Ｍ１ ｘＯｙの質量の下限は、ＦｅＮｂＯ４の質量の０％、１％、２％、３％、５％、７％、１０％、１２％又は１５％であり、上限は、５０％、４５％、４０％、３５％、３０％又は２５％である。Ｍ１ ｘＯｙの質量は、ＦｅＮｂＯ４の質量の、好ましくは０～４０％、より好ましくは１０～３０％、さらに好ましくは１５～２５％である。 The carrier of the present invention is composed of FeNbO 4 and M 1 x O y (M 1 , x, and y are as defined above). The mass of M 1 x O y is 0 to 50% of the mass of FeNbO 4 . The lower limit of the mass of M 1 x O y is 0%, 1%, 2%, 3%, 5%, 7%, 10%, 12% or 15% of the mass of FeNbO 4 , and the upper limit is 50% 45%, 40%, 35%, 30% or 25%. The mass of M 1 x O y is preferably 0 to 40%, more preferably 10 to 30%, and further preferably 15 to 25% of the mass of FeNbO 4 .
　Ｍ１ ｘＯｙの質量がＦｅＮｂＯ４の質量の０％の場合、本発明の排ガス浄化用鉄系複合酸化物触媒は、Ｍ／ＦｅＮｂＯ４になる。 When the mass of M 1 x O y is 0% of the mass of FeNbO 4 , the iron-based composite oxide catalyst for exhaust gas purification of the present invention becomes M / FeNbO 4 .
　Ｍ１ ｘＯｙの質量には最適値が存在し、多すぎるとＮＯの変換効率が低下する。 There is an optimum value for the mass of M 1 x O y , and if it is too much, the conversion efficiency of NO decreases.
　Ｍ１ ｘＯｙの質量がＦｅＮｂＯ４の質量の０％を超えて５０％以下の場合、ＦｅＮｂＯ４とＭ１ ｘＯｙは焼成により同時に生成してもよいが、ＦｅＮｂＯ４にＦｅ化合物又はＭｎ化合物を担持させ、焼成することでＦｅＮｂＯ４とＭ１ ｘＯｙ（Ｍ１、ｘ、ｙは前記に定義されるとおりである）から構成される本発明の複合酸化物担体を製造することが可能である。 M 1 x O when y mass is less than 50% greater than 0% of the mass of FeNbO 4 of, FeNbO 4 and M 1 x O y may be generated simultaneously by firing but, Fe compound FeNbO 4 or Mn A composite oxide carrier of the present invention composed of FeNbO 4 and M 1 x O y (M 1 , x, and y are as defined above) can be produced by supporting and firing a compound. Is possible.
　Ｍ１ ｘＯｙの質量がＦｅＮｂＯ４の質量の０％を超えて５０％以下の場合、Ｍ１ ｘＯｙ／ＦｅＮｂＯ４で表される複合酸化物担体は、Ｆｅ化合物又はＭｎ化合物を含む溶液にＦｅＮｂＯ４を含浸もしくは浸漬し、或いはＦｅＮｂＯ４にＦｅ化合物又はＭｎ化合物を含む溶液をスプレー等で塗布することにより接触させ、その後、焼成することにより製造することができる。Ｆｅ化合物としては、硝酸塩、酢酸塩などの有機酸塩、炭酸塩、ハロゲン化物（フッ化物、塩化物、臭化物、ヨウ化物）などが挙げられ、アセチルアセトン、アルコキシド（メトキシド、エトキシド、ｔｅｒｔ－ブトキシドなど）のような配位子が配位した錯体化合物、酢酸塩等の有機酸塩、硝酸塩が好ましく使用できる。Ｍｎ化合物としては、硝酸塩、酢酸塩などの有機酸塩、炭酸塩、ハロゲン化物（フッ化物、塩化物、臭化物、ヨウ化物）などが挙げられ、アセチルアセトン、アルコキシド（メトキシド、エトキシド、ｔｅｒｔ－ブトキシドなど）のような配位子が配位した錯体化合物、酢酸塩等の有機酸塩、硝酸塩が好ましく使用できる。焼成温度としては、４００℃～１０００℃程度、好ましくは５００～７００℃程度である。焼成時間は、１０分から２４時間程度、好ましくは３０分～５時間程度である。焼成は空気流通下で行うことができる。 M 1 x O when y mass is less than 50% greater than 0% of the mass of FeNbO 4 of the solution composite oxide support, containing Fe compound or a Mn compound represented by M 1 x O y / FeNbO 4 It can be manufactured by impregnating or immersing FeNbO 4 in or by applying a solution containing Fe compound or Mn compound to FeNbO 4 by spraying, and then firing. Examples of Fe compounds include organic acid salts such as nitrates and acetates, carbonates, halides (fluorides, chlorides, bromides, iodides), acetylacetone, alkoxides (methoxide, ethoxide, tert-butoxide, etc.) A complex compound in which a ligand is coordinated, an organic acid salt such as acetate, and a nitrate can be preferably used. Examples of Mn compounds include organic acid salts such as nitrates and acetates, carbonates, halides (fluorides, chlorides, bromides, iodides), acetylacetone, alkoxides (methoxide, ethoxide, tert-butoxide, etc.) A complex compound in which a ligand is coordinated, an organic acid salt such as acetate, and a nitrate can be preferably used. The firing temperature is about 400 ° C. to 1000 ° C., preferably about 500 to 700 ° C. The firing time is about 10 minutes to 24 hours, preferably about 30 minutes to 5 hours. Firing can be performed under air flow.
　本発明の一般式（Ｉ）で表される触媒は、貴金属化合物を含む溶液にＭ１ ｘＯｙ／ＦｅＮｂＯ４（Ｍ１、ｘ、ｙは前記に定義されるとおりである。Ｍ１ ｘＯｙの質量はＦｅＮｂＯ４の質量の０～５０％である。）で表わされる複合酸化物担体を含浸もしくは浸漬し、或いは前記担体に貴金属化合物を含む溶液をスプレー等で塗布することにより接触させ、その後、焼成することにより製造することができる。貴金属化合物としては、ヘキサクロロ白金酸、テトラクロロ白金酸、テトラクロロ白金酸カリウム、テトラクロロ白金酸ナトリウム、塩化白金、ジニトロジアミン白金などの白金化合物；塩化パラジウム、硝酸パラジウム、硫酸パラジウム，酢酸パラジウムなどのパラジウム化合物；塩化ロジウム、硫酸ロジウム、硝酸ロジウム、水酸化ロジウム，アセチルアセトナトロジウムなどのロジウム化合物が挙げられる。焼成温度としては、４００℃～１０００℃程度、好ましくは５００～７００℃程度である。焼成時間は、１０分から２４時間程度、好ましくは３０分～５時間程度である。焼成は空気流通下で行うことができる。 Catalyst represented by the general formula (I) of the present invention, the solution containing the noble metal compound M 1 x O y / FeNbO 4 (M 1, x, y are as defined above .M 1 x O The mass of y is 0 to 50% of the mass of FeNbO 4 ). The composite oxide carrier represented by (2) is impregnated or immersed, or a solution containing a noble metal compound is applied to the carrier by spraying or the like. Then, it can manufacture by baking. As noble metal compounds, platinum compounds such as hexachloroplatinic acid, tetrachloroplatinic acid, potassium tetrachloroplatinate, sodium tetrachloroplatinate, platinum chloride, dinitrodiamineplatinum; palladium chloride, palladium nitrate, palladium sulfate, palladium acetate, etc. Palladium compounds; rhodium compounds such as rhodium chloride, rhodium sulfate, rhodium nitrate, rhodium hydroxide and acetylacetonatodium. The firing temperature is about 400 ° C. to 1000 ° C., preferably about 500 to 700 ° C. The firing time is about 10 minutes to 24 hours, preferably about 30 minutes to 5 hours. Firing can be performed under air flow.
　本発明の触媒は、ＣＯ、炭化水素（ＨＣ）、ＮＯｘをリーンバーン条件で処理できるので、自動車排ガス浄化用の三元触媒として特に優れている。 Since the catalyst of the present invention can treat CO, hydrocarbon (HC) and NOx under lean burn conditions, it is particularly excellent as a three-way catalyst for automobile exhaust gas purification.
　以下、本発明を実施例を用いてより詳細に説明するが、本発明がこれら実施例に限定されないことはいうまでもない。 Hereinafter, although the present invention will be described in more detail with reference to examples, it goes without saying that the present invention is not limited to these examples.
参考製造例１：ＦｅＮｂＯ４の調製
　Ｆｅ（ＮＯ３）３・９Ｈ２Ｏ（１０ｍｍｏｌ）およびＮｂＣｌ５（１０ｍｍｏｌ）をクエン酸２００ｍｍｏｌを含むメタノール（１８０ｍｌ）に溶解させた。この溶液を室温で３０分間撹拌後，エチレングリコール（４００ｍｍｏｌ）を加え８０℃で５ｈ撹拌することでゲル状生成物を得た。このゲル状生成物を３５０℃で３ｈ焼成し粉末とした後に，さらに５００℃で５ｈ焼成することでα-ＰｂＯ2型構造を有するＦｅＮｂＯ４を約２ｇ得た。 Reference Production Example 1: FeNbO 4 Preparation Fe (NO 3) 3 · 9H 2 O (10mmol) and NbCl 5 (10 mmol) was dissolved in methanol (180 ml) containing citric acid 200 mmol. After stirring this solution at room temperature for 30 minutes, ethylene glycol (400 mmol) was added and stirred at 80 ° C. for 5 hours to obtain a gel product. This gel product was calcined at 350 ° C. for 3 hours to obtain powder, and further calcined at 500 ° C. for 5 h to obtain about 2 g of FeNbO 4 having an α-PbO 2 type structure.
実施例１
　参考製造例１で得たＦｅＮｂＯ４に対し、焼成後のＦｅ２Ｏ３の量が１０質量％、２０質量％、３０質量％、５０質量％になる量のＦｅ（ＮＯ３）３・９Ｈ２Ｏを含む水溶液にＦｅＮｂＯ４（１ｇ）含浸し、５００℃で焼成し、１０　Ｆｅ２Ｏ３／ＦｅＮｂＯ４、２０　Ｆｅ２Ｏ３／ＦｅＮｂＯ４、３０　Ｆｅ２Ｏ３／ＦｅＮｂＯ４、５０　Ｆｅ２Ｏ３／ＦｅＮｂＯ４、で表わされる複合酸化物担体を得た。
　得られたＸ　Ｆｅ２Ｏ３／ＦｅＮｂＯ４、（Ｘ＝１０，２０，３０，５０）（０．９９ｇ）に対しＲｈ（ｍｅｔａｌ）が１ｗｔ％となるようにロジウムアセチルアセトナート（ＩＩＩ）（Ｒｈ（ａｃａｃ）３，　０．０４０１ｇ）の酢酸エチル９ｍｌ溶液に室温にて含浸担持し，乾燥後，空気中５００℃にて３０分間焼成することで、１ｗｔ％Ｒｈ／（Ｘ　Ｆｅ２Ｏ３／ＦｅＮｂＯ４）　（Ｘ＝１０，２０，３０，５０）を得た。 Example 1
To FeNbO 4 obtained in Reference Production Example 1, the amount is 10 mass% of Fe 2 O 3 after firing 20 wt%, 30 wt%, the amount of Fe (NO 3) becomes 50 mass% 3 · 9H 2 An aqueous solution containing O is impregnated with FeNbO 4 (1 g), fired at 500 ° C., 10 Fe 2 O 3 / FeNbO 4 , 20 Fe 2 O 3 / FeNbO 4 , 30 Fe 2 O 3 / FeNbO 4 , 50 Fe 2 O A composite oxide carrier represented by 3 / FeNbO 4 was obtained.
Rhodium acetylacetonate (III) (Rh) so that Rh (metal) is 1 wt% with respect to the obtained X 2 Fe 2 O 3 / FeNbO 4 (X = 10, 20, 30, 50) (0.99 g). (Acac) 3 , 0.0401 g) in 9 ml of ethyl acetate is impregnated and supported at room temperature, dried, and then calcined in air at 500 ° C. for 30 minutes to obtain 1 wt% Rh / (X Fe 2 O 3 / FeNbO 4 ) (X = 10, 20, 30, 50) was obtained.
比較例１
　γ－Ａｌ２Ｏ３（参照触媒ＡＬＯ－７（１８０ｍ２／ｇ），触媒学会提供、０．９９ｇ）に対しＲｈが金属として１．０ｗｔ％となるようにロジウムアセチルアセトナート（ＩＩＩ）（Ｒｈ（ａｃａｃ）３，　０．０４０１ｇ）の酢酸エチル９ｍｌ溶液に含浸担持し，乾燥後，空気中５００℃にて３０分間焼成することで１ｗｔ％Ｒｈ／Ａｌ２Ｏ３を得た。 Comparative Example 1
Rhodium acetylacetonate (III) (Rh) so that Rh is 1.0 wt% as a metal with respect to γ-Al 2 O 3 (reference catalyst ALO-7 (180 m 2 / g), provided by the Catalysis Society of Japan, 0.99 g). (Acac) 3 , 0.0401 g) was impregnated and supported in a 9 ml ethyl acetate solution, dried, and then calcined in air at 500 ° C. for 30 minutes to obtain 1 wt% Rh / Al 2 O 3 .
比較例２～６
　使用する金属酸化物触媒を変更する以外は比較例１と同様の手法で１ｗｔ％Ｒｈ／Ｆｅ２Ｏ３（比較例３）、１ｗｔ％Ｒｈ／２０Ｆｅ２Ｏ３／ＣｅＯ２（比較例４）、１ｗｔ％Ｒｈ／２０Ｆｅ２Ｏ３／ＺｒＯ２（比較例５）、１ｗｔ％Ｒｈ／２０Ｆｅ２Ｏ３／Ａｌ２Ｏ３（比較例６）を調製した。 Comparative Examples 2-6
1 wt% Rh / Fe 2 O 3 (Comparative Example 3), 1 wt% Rh / 20Fe 2 O 3 / CeO 2 (Comparative Example 4) in the same manner as in Comparative Example 1 except that the metal oxide catalyst used is changed. 1 wt% Rh / 20Fe 2 O 3 / ZrO 2 (Comparative Example 5) and 1 wt% Rh / 20Fe 2 O 3 / Al 2 O 3 (Comparative Example 6) were prepared.
試験例１
　比較例１、２で得られた１ｗｔ％Ｒｈ／Ａｌ２Ｏ３と１ｗｔ％Ｒｈ／ＦｅＮｂＯ４の触媒について、図１に概略的に示す常圧固定床流通型反応装置を用いて反応を行った。
　触媒（２００ｍｇ）を石英反応管に充填し，前処理としてＨｅを３０　ｍＬ　ｍｉｎ－１，５００℃で１ｈ流通させた。反応ガスとしてＮＯ：　１０００ｐｐｍ，ＣＯ：　１０００ｐｐｍ，Ｃ３Ｈ６：　２５０ｐｐｍ，Ｏ２：　（１４６２ｐｐｍ→１１２５ｐｐｍ→６７５ｐｐｍ→１１２５ｐｐｍ→１４６２ｐｐｍ），Ｈｅ：　ｂａｌａｎｃｅの混合ガスを１００　ｍＬ　ｍｉｎ－１で触媒層に流通させた。なお，化学両論量の酸素濃度は１１２５ｐｐｍであり，酸素濃度変動させる実験において，ＮＯ，ＣＯおよびＣ３Ｈ６の濃度は固定した。出口ガス分析は高酸素濃度から低酸素濃度に変化させ，再び高酸素濃度に変動させた際の各酸素濃度条件で３０ｍｉｎ保持した後に出口ガス分析を行った。反応ガスの分析は２台のＴＣＤ－ＧＣ８Ａ（Ｓｈｉｍａｄｚｕ製　ＭＳ－５Ａ及びＰｏｒａｐａｋ　Ｑ）により行った。２台のＴＣＤ－ＧＣ８Ａ（ＭＳ－５Ａ及びＰｏｒａｐａｋ　Ｑ）によりＣ３Ｈ６、ＣＯ、ＣＯ２、Ｎ２、Ｎ２Ｏを測定し、ＮＯからＮ２への変換効率を求めた。結果を図２に示す。
　図２の結果から、Ｒｈ／ＦｅＮｂＯ４の触媒は、リッチバーン（λ＝０．７９）の後にリーンバーン（λ＝１．１６）を行うと、ＮＯからＮ２への変換率が向上するが、Ｒｈ／Ａｌ２Ｏ３はリッチバーン（λ＝０．７９）の後にリーンバーン（λ＝１．１６）を行ってもＮＯからＮ２への変換率がほとんど変化しないことが明らかになった。 Test example 1
The 1 wt% Rh / Al 2 O 3 and 1 wt% Rh / FeNbO 4 catalysts obtained in Comparative Examples 1 and 2 were reacted using an atmospheric pressure fixed bed flow reactor schematically shown in FIG. .
A catalyst (200 mg) was filled in a quartz reaction tube, and as a pretreatment, He was allowed to flow at 30 mL min −1 at 500 ° C. for 1 h. As reaction gases, NO: 1000 ppm, CO: 1000 ppm, C 3 H 6 : 250 ppm, O 2 : (1462 ppm → 1125 ppm → 675 ppm → 1125 ppm → 1462 ppm), He: balance mixed gas is circulated to the catalyst layer at 100 mL min −1 I let you. The stoichiometric amount of oxygen was 1125 ppm, and in the experiment for varying the oxygen concentration, the concentrations of NO, CO, and C 3 H 6 were fixed. The outlet gas analysis was performed after changing from a high oxygen concentration to a low oxygen concentration and holding for 30 minutes at each oxygen concentration condition when the oxygen concentration was changed again to a high oxygen concentration. The analysis of the reaction gas was performed by two TCD-GC8A (MS-5A and Porapak Q manufactured by Shimadzu). C 3 H 6 , CO, CO 2 , N 2 and N 2 O were measured by two TCD-GC8A (MS-5A and Porapak Q), and the conversion efficiency from NO to N 2 was determined. The results are shown in FIG.
From the results shown in FIG. 2, when the Rh / FeNbO 4 catalyst is subjected to lean burn (λ = 1.16) after rich burn (λ = 0.79), the conversion rate from NO to N 2 is improved. , Rh / Al 2 O 3 was found to have almost no change in the conversion rate from NO to N 2 even when lean burn (λ = 1.16) was performed after rich burn (λ = 0.79). .
試験例２
　実施例１で得られた１ｗｔ％Ｒｈ／ＦｅＮｂＯ４と比較例１で得られた１ｗｔ％Ｒｈ／Ａｌ２Ｏ３の触媒について、図３に示される触媒を用いて試験を行った。
　触媒（２００ｍｇ）を石英反応管に充填し，前処理としてＨｅを３０　ｍＬ　ｍｉｎ－１，５００℃で１　ｈ流通させた。反応ガスとしてＮＯ：　１０００ｐｐｍ，ＣＯ：　１０００ｐｐｍ，Ｃ３Ｈ６：　２５０ｐｐｍ，Ｏ２：　１４６２ｐｐｍ（λ＝１．１６），Ｈｅ：　ｂａｌａｎｃｅの混合ガスを１００　ｍＬ　ｍｉｎ－１で触媒層に流通させ，３時間保持した。その後，酸素濃度を６７５ｐｐｍ（λ＝０．７９）に変化させ３時間保持し，再び酸素濃度を１４６２ｐｐｍ（λ＝１．１６）に変化させた。出口ガス分析は３０　ｍｉｎ毎に行った。反応ガスの分析は２台のＴＣＤ－ＧＣ８Ａ（Ｓｈｉｍａｄｚｕ製　ＭＳ－５Ａ及びＰｏｒａｐａｋ　Ｑ）により行った。２台のＴＣＤ－ＧＣ８Ａ（ＭＳ－５Ａ及びＰｏｒａｐａｋ　Ｑ）によりＣ３Ｈ６、ＣＯ、ＣＯ２、Ｎ２、Ｎ２Ｏを測定し、ＮＯからＮ２への変換効率を求めた。結果を図３に示す。本実験条件に於いても，リッチ条件を経験させたＲｈ／ＦｅＮｂＯ４はリーン条件下において高い活性を維持した。そこで，以後の図には，リッチ条件を経験させた触媒のリーン条件下での触媒活性の劣化挙動を評価した。 Test example 2
The 1 wt% Rh / FeNbO 4 obtained in Example 1 and the 1 wt% Rh / Al 2 O 3 catalyst obtained in Comparative Example 1 were tested using the catalyst shown in FIG.
A catalyst (200 mg) was filled in a quartz reaction tube, and as a pretreatment, He was allowed to flow at 30 mL min −1 at 500 ° C. for 1 h. As a reaction gas, a mixed gas of NO: 1000 ppm, CO: 1000 ppm, C 3 H 6 : 250 ppm, O 2 : 1462 ppm (λ = 1.16), He: balance was circulated through the catalyst layer at 100 mL min −1 , 3 Held for hours. Thereafter, the oxygen concentration was changed to 675 ppm (λ = 0.79) and held for 3 hours, and the oxygen concentration was changed to 1462 ppm (λ = 1.16) again. Outlet gas analysis was performed every 30 min. The analysis of the reaction gas was performed by two TCD-GC8A (MS-5A and Porapak Q manufactured by Shimadzu). C 3 H 6 , CO, CO 2 , N 2 and N 2 O were measured by two TCD-GC8A (MS-5A and Porapak Q), and the conversion efficiency from NO to N 2 was determined. The results are shown in FIG. Even in this experimental condition, Rh / FeNbO 4 that experienced the rich condition maintained high activity under the lean condition. Therefore, in the following figures, the deterioration behavior of the catalytic activity under the lean condition of the catalyst that experienced the rich condition was evaluated.
試験例３
　実施例１で得られた１ｗｔ％Ｒｈ／ＦｅＮｂＯ４と１ｗｔ％Ｒｈ／（Ｘ　Ｆｅ２Ｏ３／ＦｅＮｂＯ４）　（Ｘ＝１０，２０，３０，５０）、比較例２～６で得られた１ｗｔ％Ｒｈ／Ｆｅ２Ｏ３、１ｗｔ％Ｒｈ／２０Ｆｅ２Ｏ３／ＣｅＯ２、１ｗｔ％Ｒｈ／２０Ｆｅ２Ｏ３／ＺｒＯ２、１ｗｔ％Ｒｈ／２０Ｆｅ２Ｏ３／Ａｌ２Ｏ３の触媒について、試験例２と同様の条件で反応を行い，図４および図５にはリッチ条件下（λ＝０．７９）を経験した後の触媒におけるリーン条件下（λ＝１．１６）での活性を示している。
　触媒（２００ｍｇ）を石英反応管に充填し，前処理としてＨｅを３０　ｍＬ　ｍｉｎ－１，５００℃で１ｈ流通させた。反応ガスとしてＮＯ：　１０００ｐｐｍ，ＣＯ：　１０００ｐｐｍ，Ｃ３Ｈ６：　２５０ｐｐｍ，Ｏ２：　１４６２ｐｐｍ（λ＝１．１６），Ｈｅ：　ｂａｌａｎｃｅの混合ガスを１００　ｍＬ　ｍｉｎ－１で触媒層に流通させ，３時間保持した。その後，酸素濃度を６７５ｐｐｍ（λ＝０．７９）に変化させ３時間保持し，再び酸素濃度を１４６２ｐｐｍ（λ＝１．１６）に変化させた。出口ガス分析は３０　ｍｉｎ毎に行った。反応ガスの分析は２台のＴＣＤ－ＧＣ８Ａ（Ｓｈｉｍａｄｚｕ製　ＭＳ－５Ａ及びＰｏｒａｐａｋ　Ｑ）により行った。２台のＴＣＤ－ＧＣ８Ａ（ＭＳ－５Ａ及びＰｏｒａｐａｋ　Ｑ）によりＣ３Ｈ６、ＣＯ、ＣＯ２、Ｎ２、Ｎ２Ｏを測定し、ＮＯからＮ２への変換効率を求めた。結果を図４および図５に示す。Ｆｅ２Ｏ３の担持量効果を検討したところ，２０質量％のＦｅ２Ｏ３を担持した１ｗｔ％Ｒｈ／Ｆｅ２Ｏ３／ＦｅＮｂＯ４が高い活性を最も長時間維持することを明らかにした。また，担体をＦｅＮｂＯ４から各種担体に変化させたところ，いずれの担体もＦｅＮｂＯ４より保持時間が低下した。 Test example 3
1 wt% Rh / FeNbO 4 obtained in Example 1 and 1 wt% Rh / (X Fe 2 O 3 / FeNbO 4 ) (X = 10, 20, 30, 50), 1 wt obtained in Comparative Examples 2 to 6 Catalysts of% Rh / Fe 2 O 3 , 1 wt% Rh / 20Fe 2 O 3 / CeO 2 , 1 wt% Rh / 20Fe 2 O 3 / ZrO 2 , 1 wt% Rh / 20Fe 2 O 3 / Al 2 O 3 were tested. The reaction was carried out under the same conditions as in Example 2. FIGS. 4 and 5 show the activity of the catalyst under lean conditions (λ = 1.16) after experiencing rich conditions (λ = 0.79). ing.
A catalyst (200 mg) was filled in a quartz reaction tube, and as a pretreatment, He was allowed to flow at 30 mL min −1 at 500 ° C. for 1 h. As a reaction gas, a mixed gas of NO: 1000 ppm, CO: 1000 ppm, C 3 H 6 : 250 ppm, O 2 : 1462 ppm (λ = 1.16), He: balance was circulated through the catalyst layer at 100 mL min −1 , 3 Held for hours. Thereafter, the oxygen concentration was changed to 675 ppm (λ = 0.79) and held for 3 hours, and the oxygen concentration was changed to 1462 ppm (λ = 1.16) again. Outlet gas analysis was performed every 30 min. The analysis of the reaction gas was performed by two TCD-GC8A (MS-5A and Porapak Q manufactured by Shimadzu). C 3 H 6 , CO, CO 2 , N 2 and N 2 O were measured by two TCD-GC8A (MS-5A and Porapak Q), and the conversion efficiency from NO to N 2 was determined. The results are shown in FIG. 4 and FIG. Was examined supporting amount effect of Fe 2 O 3, it revealed that carrying 20 wt% Fe 2 O 3 1wt% Rh / Fe 2 O 3 / FeNbO 4 is longest maintaining high activity. Further, when the carrier was changed from FeNbO 4 to various carriers, the retention time of all the carriers was lower than that of FeNbO 4 .
試験例４
　実施例１で得た１ｗｔ％Ｒｈ／ＦｅＮｂＯ４と１ｗｔ％Ｒｈ／（Ｘ　Ｆｅ２Ｏ３／ＦｅＮｂＯ４）　（Ｘ＝１０，２０，３０，５０）、比較例３で得た１ｗｔ％Ｒｈ／Ｆｅ２Ｏ３の各触媒について、ＸＲＤパターンを測定した。結果を図６に示す。２０質量％以上のＦｅ２Ｏ３を担持した１ｗｔ％Ｒｈ／Ｆｅ２Ｏ３／ＦｅＮｂＯ４において，α-ＰｂＯ2型構造を有するＦｅＮｂＯ４に加えα-Ｆｅ２Ｏ３のピークが見られた。 Test example 4
1 wt% Rh / FeNbO 4 and 1 wt% Rh / (X Fe 2 O 3 / FeNbO 4 ) (X = 10, 20, 30, 50) obtained in Example 1 and 1 wt% Rh / Fe obtained in Comparative Example 3 The XRD pattern was measured for each 2 O 3 catalyst. The results are shown in FIG. In 1 wt% Rh / Fe 2 O 3 / FeNbO 4 supporting 20 mass% or more of Fe 2 O 3 , a peak of α-Fe 2 O 3 was observed in addition to FeNbO 4 having an α-PbO 2 type structure.
試験例５
　実施例１で得た１ｗｔ％Ｒｈ／２０　Ｆｅ２Ｏ３／ＦｅＮｂＯ４、比較例３で得た１ｗｔ％Ｒｈ／Ｆｅ２Ｏ３、参考製造例１で得たＦｅＮｂＯ４とα-Ｆｅ２Ｏ３を重量比８０：２０で物理混合した担体に１ｗｔ％のＲｈを担持した触媒について，試験例２と同様の条件で反応を行い，図７にはリッチ条件下（λ＝０．７９）を経験した後の触媒におけるリーン条件下（λ＝１．１６）での活性を示している。
　触媒（２００ｍｇ）を石英反応管に充填し，前処理としてＨｅを３０　ｍＬ　ｍｉｎ－１，５００℃で１　ｈ流通させた。反応ガスとしてＮＯ：　１０００ｐｐｍ，ＣＯ：　１０００ｐｐｍ，Ｃ３Ｈ６：　２５０ｐｐｍ，Ｏ２：　１４６２ｐｐｍ（λ＝１．１６），Ｈｅ：　ｂａｌａｎｃｅの混合ガスを１００　ｍＬ　ｍｉｎ－１で触媒層に流通させ，３時間保持した。その後，酸素濃度を６７５ｐｐｍ（λ＝０．７９）に変化させ３時間保持し，再び酸素濃度を１４６２ｐｐｍ（λ＝１．１６）に変化させた。出口ガス分析は３０ｍｉｎ毎に行った。反応ガスの分析は２台のＴＣＤ－ＧＣ８Ａ（Ｓｈｉｍａｄｚｕ製　ＭＳ－５Ａ及びＰｏｒａｐａｋ　Ｑ）により行った。２台のＴＣＤ－ＧＣ８Ａ（ＭＳ－５Ａ及びＰｏｒａｐａｋ　Ｑ）によりＣ３Ｈ６、ＣＯ、ＣＯ２、Ｎ２、Ｎ２Ｏを測定し、ＮＯからＮ２への変換効率を求めた。結果を図７に示す。物理混合した触媒に比べ，含浸担持でＦｅＮｂＯ４にＦｅ２Ｏ３を担持した方が高い活性を維持することが明らかとなった。 Test Example 5
Obtained in Example 1 was 1wt% Rh / 20 Fe 2 O 3 / FeNbO 4, Comparative Example 3 1 wt% was obtained at a Rh / Fe 2 O 3, FeNbO 4 and α-Fe 2 O 3 obtained in Reference Production Example 1 A catalyst in which 1 wt% Rh is supported on a support physically mixed at a weight ratio of 80:20 was reacted under the same conditions as in Test Example 2, and FIG. 7 experienced rich conditions (λ = 0.79). It shows the activity of the catalyst under lean conditions (λ = 1.16).
A catalyst (200 mg) was filled in a quartz reaction tube, and as a pretreatment, He was allowed to flow at 30 mL min −1 at 500 ° C. for 1 h. As a reaction gas, a mixed gas of NO: 1000 ppm, CO: 1000 ppm, C 3 H 6 : 250 ppm, O 2 : 1462 ppm (λ = 1.16), He: balance was circulated through the catalyst layer at 100 mL min −1 , 3 Held for hours. Thereafter, the oxygen concentration was changed to 675 ppm (λ = 0.79) and held for 3 hours, and the oxygen concentration was changed to 1462 ppm (λ = 1.16) again. The outlet gas analysis was performed every 30 minutes. The analysis of the reaction gas was performed by two TCD-GC8A (MS-5A and Porapak Q manufactured by Shimadzu). C 3 H 6 , CO, CO 2 , N 2 and N 2 O were measured by two TCD-GC8A (MS-5A and Porapak Q), and the conversion efficiency from NO to N 2 was determined. The results are shown in FIG. It was revealed that FeNbO 4 with Fe 2 O 3 supported by impregnation supported higher activity than impregnated catalyst.
試験例６
　実施例１で得た１ｗｔ％Ｒｈ／２０　Ｆｅ２Ｏ３／ＦｅＮｂＯ４、比較例３で得た１ｗｔ％Ｒｈ／Ｆｅ２Ｏ３、参考製造例１で得たＦｅＮｂＯ４と・α－Ｆｅ２Ｏ３を重量比８０：２０で物理混合した担体に１ｗｔ％のＲｈを担持した触媒について，ＸＲＤパターンを測定した。結果を図８に示す。物理混合した触媒に比べ，含浸担持でＦｅＮｂＯ４にＦｅ２Ｏ３を担持した方がＦｅ２Ｏ３のピーク強度は小さく，ナノサイズのＦｅ２Ｏ３をＦｅＮｂＯ４に担持することが高い活性を維持する要因の一つであることが示唆された。 Test Example 6
Example 1 In 1wt% Rh / 20 Fe 2 O 3 / FeNbO 4 obtained in Comparative Example 3 1 wt% was obtained at a Rh / Fe 2 O 3, and FeNbO 4 obtained in Reference Production Example 1 · α-Fe 2 O An XRD pattern was measured for a catalyst in which 1 wt% Rh was supported on a support obtained by physically mixing 3 in a weight ratio of 80:20. The results are shown in FIG. Compared to the physical mixture catalyst, the peak intensity of the person carrying the Fe 2 O 3 in FeNbO 4 impregnated carrier is Fe 2 O 3 is small, the high activity of carrying a Fe 2 O 3 nano-sized FeNbO 4 It was suggested that this is one of the factors to maintain.
試験例７
　実施例１で得た１ｗｔ％Ｒｈ／ＦｅＮｂＯ４と１ｗｔ％Ｒｈ／２０　Ｆｅ２Ｏ３／ＦｅＮｂＯ４、比較例３で得た１ｗｔ％Ｒｈ／Ｆｅ２Ｏ３触媒について，酸素貯蔵能測定を行った。
　触媒（１００　ｍｇ）を熱重量分析（Ｒｉｇａｋｕ製　ＴＧ－８２０）のアルミナセルにセットした。反応ガスとして５％Ｏ２／Ａｒを１００　ｍＬ　ｍｉｎ－１で触媒層に流通させ，５００℃まで昇温した。５％Ｏ２／Ａｒ　雰囲気下で３０分保持後，５％Ｈ２／Ａｒを１００　ｍＬ　ｍｉｎ－１のガスに切り替え重量変化を２０分間測定した。さらに，５％Ｏ２／Ａｒを１００　ｍＬ　ｍｉｎ－１のガスに切り替え重量変化を２０分間測定した。結果を図９に示す。１ｗｔ％Ｒｈ／２０　Ｆｅ２Ｏ３／ＦｅＮｂＯ４の酸素貯蔵能は１ｗｔ％Ｒｈ／ＦｅＮｂＯ４のものより高かった。また，１ｗｔ％Ｒｈ／２０　Ｆｅ２Ｏ３／ＦｅＮｂＯ４の酸素放出速度は１ｗｔ％Ｒｈ／Ｆｅ２Ｏ３触媒より高かった。１ｗｔ％Ｒｈ／Ｆｅ２Ｏ３／ＦｅＮｂＯ４の酸素貯蔵能がリーン条件下での高い活性の維持に寄与している可能性が示唆された。 Test Example 7
The oxygen storage capacity of the 1 wt% Rh / FeNbO 4 and 1 wt% Rh / 20 Fe 2 O 3 / FeNbO 4 obtained in Example 1 and the 1 wt% Rh / Fe 2 O 3 catalyst obtained in Comparative Example 3 was measured. .
The catalyst (100 mg) was set in an alumina cell for thermogravimetric analysis (TG-820, manufactured by Rigaku). 5% O 2 / Ar as a reaction gas was passed through the catalyst layer at 100 mL min −1 and the temperature was raised to 500 ° C. After holding in a 5% O 2 / Ar atmosphere for 30 minutes, 5% H 2 / Ar was switched to a gas of 100 mL min −1 and the change in weight was measured for 20 minutes. Furthermore, 5% O 2 / Ar was switched to a gas of 100 mL min −1 and the change in weight was measured for 20 minutes. The results are shown in FIG. The oxygen storage capacity of 1 wt% Rh / 20 Fe 2 O 3 / FeNbO 4 was higher than that of 1 wt% Rh / FeNbO 4 . Further, the oxygen release rate of 1 wt% Rh / 20 Fe 2 O 3 / FeNbO 4 was higher than that of the 1 wt% Rh / Fe 2 O 3 catalyst. It was suggested that the oxygen storage capacity of 1 wt% Rh / Fe 2 O 3 / FeNbO 4 may contribute to maintaining high activity under lean conditions.

Claims (5)

  1. 下記式（Ｉ）
    　Ｍ／Ｍ１ ｘＯｙ／ＦｅＮｂＯ４　　　（Ｉ）
    （式中、ＭはＰｄ、Ｒｈ及びＰｔからなる群から選ばれる少なくとも１種の貴金属を示す。Ｍ１は、ＭｎもしくはＦｅを示す。ｘは１～３の整数を示し、ｙは２～４の整数を示す。ｘが１のときはｙが２であり，ｘが２のときはｙが３であり，ｘが３のときはｙが４である。Ｍ１ ｘＯｙの質量はＦｅＮｂＯ４の質量の０～５０％である。Ｍは、Ｍ１ ｘＯｙ／ＦｅＮｂＯ４に担持されている。）
    で表わされる、排ガス浄化用鉄系複合酸化物触媒。     Formula (I)
    M / M 1 x O y / FeNbO 4 (I)
    (In the formula, M represents at least one noble metal selected from the group consisting of Pd, Rh and Pt. M 1 represents Mn or Fe. X represents an integer of 1 to 3, and y represents 2 to 4. When x is 1, y is 2, when x is 2, y is 3, and when x is 3, y is 4. The mass of M 1 x O y is FeNbO. 0 to 50% of the mass of 4. M is supported on M 1 x O y / FeNbO 4 )
    An iron-based composite oxide catalyst for exhaust gas purification represented by
  2. ＭがＲｈである、請求項１に記載の排ガス浄化用鉄系複合酸化物触媒。 The iron-based composite oxide catalyst for exhaust gas purification according to claim 1, wherein M is Rh.
  3. Ｍ１ ｘＯｙがＦｅ２Ｏ３である、請求項１又は２に記載の排ガス浄化用鉄系複合酸化物触媒。 The iron-based composite oxide catalyst for exhaust gas purification according to claim 1 or 2, wherein M 1 x O y is Fe 2 O 3 .
  4. Ｆｅ２Ｏ３の質量はＦｅＮｂＯ４の質量の１５～２５％である、請求項３に記載の排ガス浄化用鉄系複合酸化物触媒。 The iron-based composite oxide catalyst for exhaust gas purification according to claim 3, wherein the mass of Fe 2 O 3 is 15 to 25% of the mass of FeNbO 4 .
  5. Ｍ１ ｘＯｙ／ＦｅＮｂＯ４（Ｍ１は、ＭｎもしくはＦｅを示す。ｘは１～３の整数を示し、ｙは２～４の整数を示す。ｘが１のときはｙが２であり，ｘが２のときはｙが３であり，ｘが３のときはｙが４である。Ｍ１ ｘＯｙの質量はＦｅＮｂＯ４の質量の０～５０％である。）で表わされる複合酸化物担体をＰｄ化合物、Ｐｔ化合物及びＲｈ化合物の少なくとも１種を含む溶液に接触し、焼成する工程
    を含む、下記式（Ｉ）
    　Ｍ／Ｍ１ ｘＯｙ／ＦｅＮｂＯ４　　　（Ｉ）
    （式中、ＭはＰｄ、Ｒｈ及びＰｔからなる群から選ばれる少なくとも１種の貴金属を示す。Ｍ１ ｘＯｙは前記に定義されるとおりである。Ｍ１ ｘＯｙの質量はＦｅＮｂＯ４の質量の０～５０％である。Ｍは、Ｆｅ２Ｏ３／ＦｅＮｂＯ４に担持されている。）
    で表わされる、排ガス浄化用鉄系複合酸化物触媒の製造方法。     M 1 x O y / FeNbO 4 (M 1 represents Mn or Fe. X represents an integer of 1 to 3, y represents an integer of 2 to 4. When x is 1, y is 2. , When x is 2, y is 3, and when x is 3, y is 4. The mass of M 1 x O y is 0 to 50% of the mass of FeNbO 4 ). The step of bringing the oxide carrier into contact with a solution containing at least one of a Pd compound, a Pt compound and an Rh compound, followed by firing, is carried out by the following formula (I)
    M / M 1 x O y / FeNbO 4 (I)
    (Wherein M represents at least one noble metal selected from the group consisting of Pd, Rh and Pt. M 1 x O y is as defined above. The mass of M 1 x O y is FeNbO 4. (M is supported on Fe 2 O 3 / FeNbO 4. )
    The manufacturing method of the iron type complex oxide catalyst for exhaust gas purification represented by these.
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